This invention relates generally to the use of a laser in aligning tubular assemblies and more particularly to laser alignment and marking of a Mule-shoe sub containing an orienting sleeve, relative to the mud-motor orientation in an oil and gas well directional drilling operation.
Oil and gas well drilling operation often utilizes directional drilling technology whereby a drill string extends into a substantially vertical well bore and generally supports a hydraulically operated motor and drill bit at its lower end. Angular drilling is produced by using a bent sub or downhole motor with a bent housing. A directional measurement tool is generally connected above the drill or mud motor to provide a method of steering the drill string. An orienting sub is connected to the directional measurement tool for orienting the position of the directional measurement tool relative to the motor. The orienting sub is generally a tubular construction with a connection to the directional measurement tool at one end and a connection to the bent sub or the upper motor housing at the other end. The orienting sub has a sleeve mounted within the sub""s bore containing an internal key utilized to receive a mule shoe for locating the directional measurement tool in relation to the drill motor. The directional measurement equipment, to which the mule shoe arrangement is connected, generally includes an axially extending slot that communicates at its lower end with a camming surface. A butting engagement of the key with the camming surface rotates the directional measurement assembly to permit the slot therein to receive the key. When the slot and key are fully engaged, the measurement equipment is accurately oriented with respect to the motor or bent sub so that it may accurately plot or record the orientation at which the key, and therefore the motor or bent sub, are disposed relative to a predetermined datum.
Orientation of the measuring or directional/logging equipment orientation sleeve located and locked inside the orienting sub, relative to the orienting sub and in alignment with the bent housing orientation of the drill motor, is achieved upon establishment of the bottom hole assembly. The directional drilling string assembly consists of a drill bit, an adjustable, bent housing, steerable drilling motor, a float sub, a crossover and/or stabilizer (if applicable), a mule shoe sub containing the above mentioned locked in orienting sleeve, and a non-magnetic drill collar used to house the directional/logging equipment.
At assembly of the directional drilling string, the directional driller sets the Drill Motor orientation to the prescribed bend, based on the drilling application for the well being drilled. Once the Drill Motor""s bent housing orientation has been set, a scribe-line is marked externally on the motor housing and extended by a straight edge or by sight along the length of the string extending over several feet and crossing connecting joints to a point adjacent the orientating sleeve located inside the orientating sub. The orientation sleeve is then rotatably adjusted for alignment with the scribe line by using a hand tool configured to be inserted internally through the bore of the mule-shoe sub to engage a key located integral with the orientation sleeve. Since the orienting process must be repeated several times while drilling a deviated hole and the scribe lines are hard to see, especially at night, and originate at a point on the mud motor housing that is usually below the rig floor and submerged in mud when the orienting sleeve is being adjusted, it is very difficult, if not impossible, to maintain any degree of accurate alignment. Even an unrecognizable surface deviation in the scribe line resulting in only a minor difference between the logging measurement equipment orientation and the mud motor orientation produces a significant deviation in the subsurface course plan extending over several hundred feet. Such a deviation of only a few degrees either way can spell the difference between achieving an accurate well target location or ending with a dry hole. Therefore, there is a need for a more precise method of aligning and marking the mule shoe sub for orientation with the measuring and logging equipment alignment sleeve.
Although lasers have been used extensively to help align instruments used in pipe lines, the alignment and mating of pipe sections and the positioning of tubing in pressed ahead directional drilling operations, there is no indication that lasers have been used in the drilling environment where conditions are more hostile to the use of such equipment, i.e. at night, in all kinds of weather, and under wet and/or oily conditions. Secondly, there is a need to provide a means for providing a reference mark on or adjacent to the upper end of the orientation sub that is in precise alignment with the mud motor""s bent sub orientations so that the mule-shoe sub""s orientation sleeve can be precisely aligned when the string is in a vertical position with the mud motor submerged in mud and/or located below the rig floor.
A laser alignment tool used in directional drilling operations for aligning and orienting and marking directional and/or logging equipment relative to the setting of an adjustable, bent housing, drilling motor assembly. The tool includes a laser beam transmitter mountable over the scribe line of the drill motor and a laser capture and marking band located adjacent the adjustable orienting sleeve located within the mule shoe orienting sub.
In operation the laser unit is attached externally to the bent housing of the drill motor and aligned parallel with the orienting scribe mark setting of the drill motor. An adjustable capture band, including a photo sensitive film, paper band, or photo sensitive resin paste, is attached or applied directly to the upper potion of the mule shoe or orienting sub adjacent the measuring or logging instrument orienting sleeve. The means for marking also includes a prism or mirror for directing the laser beam through a mask producing an elongated mark onto the photosensitive paste or film.